In mobile communication networks, e.g., according to the technical specifications (TSs) of the Third Generation Partnership Project (3GPP), concepts have been introduced according to which several carriers operated in different frequency channels can be bundled in a single radio link. These concepts are also referred to as carrier aggregation.
For example, in 3GPP Long Term Evolution (LTE) Release 10, in the following also referred to as LTE Rel-10, carrier aggregation implies aggregation of multiple component carriers of narrower bandwidth. Each backward compatible component carrier would then, to an LTE terminal, appear as and provide all the capabilities of an LTE carrier. At the same time, an
LTE Rel-10 terminal would be able to access the entire aggregation of multiple carriers, thus experiencing an overall wider bandwidth with corresponding possibilities for higher data rates. Note that carrier aggregation may be useful also for a total bandwidth below 20 MHz, e.g., for a pair of 5 MHz carriers. Sometimes component carriers are also referred to as cells, more specifically as primary cell (Pcell) and secondary cells (Scell).
The aggregated component carriers may be adjacent to each other. However, in more general terms the carrier aggregation may also allow for non-adjacent component carriers, including carriers in different frequency bands, or both adjacent and non-adjacent component carriers. Thus, the introduction of carrier aggregation as part of LTE Rel-10 allows for spectrum aggregation, i.e., the simultaneous usage of different non-contiguous spectrum fragments for communication in a downlink (DL) direction to a single mobile terminal or in an uplink (UL) direction from a single mobile terminal.
In 3GPP LTE Release 8, in the following also referred to as LTE Rel-8, a radio base station referred to as evolved Node B (eNB) and the mobile terminal use control elements (CEs) of a Medium Access Control (MAC) protocol to exchange control information such as buffer status reports, power headroom reports and others. A list of MAC CEs is provided in section 6.1.3 of 3GPP TS 36.321, “Evolved Universal Terrestrial Radio Access (E-UTRA), Medium Access Control (MAC) protocol specification”, which is incorporated herein by reference. However, these known ways of exchanging information do not address the carrier aggregation scenario of LTE Rel-10, in which information exchange with respect to a plurality of different carriers may be necessary.
Accordingly, there is a need for techniques which allow for efficiently conveying control information between nodes which are transmitting data via a plurality of carriers.